单选题Computer Mouse The basic computer mouse is an amazingly clever invention with a relatively simple design that allows US to point at things on the computer and it is very productive. Think of all the things you can do with a mouse like selecting text for copying and pasting, drawing, and even scrolling on the page with the newer mice with the wheel. Most of us use the computer mouse daily without stopping to think how it works until it gets dirty and we have to learn how to clean it. we learn to point at things before we learn to speak, So the mouse is a very natural pointing device. Other computer pointing devices include light pens, graphics tablets and touch screens, but the mouse isstill our workhorse. The computer mouse was invented in 1964 by Douglas Englehart of Stanford University. As computer screens became more popular and arrow keys were used to move around a body of text, it became clear that a pointing device that allowed easier motion through the text and even selection of text would be very useful. The introduction of the mouse, with the Apple Lisa computer in 1983, really started the computer public on the road to relying on the mouse for routine computer tasks. How does the mouse work? we have to start at the bottom, so think upside down for now. It all starts with the mouse ball. As me mouse ball in the bottom of the mouse rolls over the mouse pad, it presses against and turns two shafts. The shafts are connected to wheels with several small holes in them. The wheels have a pair of small electronic light-emitting devices called light-emitting diodes(LED) mounted on either side. One LED sends a light beam to the LED on the other side. As the wheels spin and a hole rotates by, the light beam gets through to the LED on the other side. But a moment later the light beam is blocked until the next hole is in place. The LED detect a changing pattern of fight, converts the pattern into an electronic signal, and sends the signal to the computer through wires in a cable that goes out of the mouse body. This cable is the tail that helps give the mouse its name. The computer interprets the signal to tell it where to position the Cursor on the computer screen. So far we have only discussed the basic computer mouse that most of you probably have or have used. One problem with this design is that the mouse gets dirty as the ball rolls over the surface and picks up dirt, Eventually you have to clean your mouse. The newer optical mice avoid this problem by having no moving parts.

单选题The son was so concerned about the illness of his father.A. seriousB. happyC. luckyD. worried

单选题The story was touching .

单选题As a writer, he turned out three novels that year. A. refused B. read C. produced D. accepted

单选题{{B}}第一篇{{/B}} {{B}}Effects of Environmental Pollution{{/B}} If pollution continues to increase at the present rate, formation of aerosols (浮质) in the atmosphere will cause the onset (开始) of an ice age in about fifty year's time. This conclusion reached by Dr S. I. Rasoo1 and Dr S. H. Scheider of the United States Goddard Space Flight Center, answer the apparently conflicting questions of whether an increase in the carbon dioxide (二氧化碳) content of the atmosphere will cause the Earth warm up or increasing the aerosol question is dominant. Two specters haunting conservationists have been the prospect that environmental pollution might lead to the planet's becoming unbearably hot or cold. One of these ghosts has now been laid, because it seems that even an increase in the amount of carbon dioxide in the atmosphere to eight times its present value will produce an increase in temperature of only 2℃, which would take place over several thousand years. But the other problem now looms larger than ever. Aerosols are collection of small liquid or solid particles dispersed in air or some other medium. The particles are all so tiny that each is composed of only a few hundred atoms. Because of this they can float in the air for a very long time. Perhaps the most commonly experienced aerosol is industrial smog (烟雾) of the kind that plagued London in the 1950s and is an even greater problem in Los Angeles today. These collections of aerosols reflect the Sun's heat and thereby cause the Earth to cool. Dr Rasoo1 and Dr Schneider have calculated the exact effect of a dust aerosol layer just above the Earth's surface in the temperature of the planet. As the layer builds up, the present delicate balance between the amount of heat absorbed from the Sun and the amount radiated from the Earth is disturbed. The aerosol layer not only reflects much of the Sun's light but also transmits the infrared (红外线) radiation from below. So, while the heat input to surface drops, the loss of heat remains high until the planet cools to a new balanced state. Within fifty years, if no steps are taken to stop the spread of aerosols in the atmosphere, a cooling of the Earth by as much as 3.5~C seems inevitable. If that lasts for only a few years it would start another ice age, and because the growing ice caps at each pole would themselves reflect much of the Sun's radiation it would probably continue to develop even if the aerosol layer were destroyed. The only bright spot in this gloomy forecast lies in the hope expressed by Dr Rasoo1 and Dr Schneider that nuclear powder may replace fossil fuels in time to prevent the aerosol content of atmosphere from becoming critical.

单选题From my Ustandpoint/U, you know, this thing is just ridiculous.

单选题Agriculture made possible a more stable and a secure life. With the flourishing of agriculture, Neolithic(新石器时代的)peoples were able to free themselves out of savage life. They needn't live in caves, searching for food from dawn until dusk, chasing beasts or being chased by them. They needn't worry where to find their next meal. Agriculture made it possible for them to devote their abundant free time and energy to erecting towns and eventually cities, creating art and literature and beginning a new civilization. Indeed, they were responsible for many fundamental inventions that the modem world takes for granted. Flourishing agriculture made possible a stable and secure life becauseA. people were able to free themselves out of savage life.B. they had to worry about foods all the time.C. they had time to find new homes.D. they had more time and energy for fun.

单选题While they were away on vacation, they allowed their mail to accumulate at the post office.

单选题This is a subject that has now moved into the political domain.A. extentB. zoneC. fieldD. region

单选题I am heartily {{U}}grateful{{/U}} to your help. A. helpful B. hateful C. delightful D. thankful

单选题Nitrogen is the most plentiful gas in the atmosphere.

单选题The factory is due to be demolished next year.

单选题The Public Health System One of the biggest changes since 1990 is the degree to which bioterrorism has become a public health priority. Although there had long been concern about vulnerability to biowarfare and bioterrorism the anthrax episode in the fall of 2001 made it clear that the concern is no longer theoretical. Until very recently, the important role of public health at the frontlines of bioterrorism preparedness was unrecognized. Although concern about emerging infections has helped stimulate funding for the chronically under-appreciated public health system, the threat of bioterrorism motivated the first real infusion of new money into public health in decades. Many of the capabilities needed to defend against bioterrorism are the same: as those needed to combat natural emerging infections. In both instance, the problem is an unexpected outbreak of infectious disease, of which the first indication is likely to be sick people in emergency rooms or clinics. Indeed, as with the anthrax attacks, the public health and medical responses may be under way before the true nature of the outbreak is recognized. Public health and the interface with the health care system are therefore key elements in any effective response to bioterrorism. Whether the biggest threat is natural or engineered much remains to be done. Efforts to strengthen surveillance and response worldwide and to improve communication must be accelerated and sustained. Further, we have only scratched the surface in terms of under-standing the ecology of infections diseases and developing strategies for regulating microbial traffic. We need tools for better predictive epidemiologic modeling when a new infection first appears and for better analysis of the factors that transfer pathogens across species. One encouraging development is the program in the ecology of infectious diseases that was started a few years ago be the National Science Foundation in cooperation with NIH. SARS is a good yardstick of our progress during the past 13 years. The syndrome was unusual because novel infections that spread from person to person are relatively rare. Once cases were finally reported, the public health response was vigorous. WHO warned health care providers, researchers rapidly identified a candidate virus, and prototype diagnostic tests quickly became available. The vast reach of the Interact was instrumental in sharing in formation and coordinating activities worldwide. Despite these advances SARS had already spread to many countries. In fact had the disease been as transmissible as influenza, it would have invaded virtually every country in the world by the time the public health response had begun. So what SARS tells us is that although we have come long way since 1990, we still have a long way to go.

单选题Jim has gained so much weight that a lot of his clothes don't fit him any more. A. put off B. put down C. put on D. put up

单选题A ship was reported to be in distress a few miles out at sea. A. disorder B. formation C. service D. danger

单选题Today, many countries are__________.

单选题She was grateful to him for being so good to her.

单选题 阅读下面的短文，文中有15处空白，每处空白给出了4个选项，请根据短文的内容从 4个选项中选择1个最佳答案。 The Great Newspaper War Up until about 100 years ago, newspapers in the United States appealed only to the most serious readers. They used no illustrations and the articles were{{U}} (51) {{/U}}politics or business. Two men{{U}} (52) {{/U}}that — Joseph Pulitzer of the New York World and William Randolph Hearst of the New York Morning Journal. Pulitzer{{U}} (53) {{/U}}the New York World in 1883. He changed it from a traditional newspaper into a very (54) one overnight (一夜之间). He{{U}} (55) {{/U}}lots of illustrations and cartoons. And he told his reporters to write articles on{{U}} (56) {{/U}}crime or scandal they could find. And they did. One of them even pretended she was crazy and then she was{{U}} (57) {{/U}}to a mental hospital. She then wrote a series of articles about the poor{{U}} (58) {{/U}}of patients in those hospitals. In 1895, Hearst{{U}} (59) {{/U}}to New York from California. He wanted the New York Morning Journal to be more sensational (轰动的) and more exciting{{U}} (60) {{/U}}the New York World. He also wanted it to be cheaper, so he{{U}} (61) {{/U}}the price by a penny. Hearst attracted attention because his headlines were bigger than{{U}} (62) {{/U}}. He often said, "Big print makes big news." Pulitzer and Hearst did anything they{{U}} (63) {{/U}}to sell newspapers. For example, Hearst sent Frederic Remington, the famous illustrator (插图画家), to{{U}} (64) {{/U}}pictures of the Spanish-American War. When he got there, he told Hearst that no fighting was{{U}} (65) {{/U}}. Hearst answered, "You furnish (提供) the pictures. I'll furnish the war."

单选题It is obvious that he will win the game.

单选题Long before the concert began, big crowds of pop fans had assembled in the stadium.